of the Invention
The invention pertains to the field of cutting tools. More particularly, the invention pertains to an end mill with a plurality of tungsten carbide slugs inserted inside the end mill and one or more compression screws for compressing the slugs, thereby increasing the stiffness and rigidity of the end mill.
Description of Related Art
In general, rotary cutting tools are designed with multiple flutes spaced approximately symmetrical around the circumference of the tool where the flutes run along a partial length of the tool ending at the tool shank. The tool shank is the portion of the tool that is mounted in a machine tool and the fluted portion is the portion of the tool that engages the workpiece. The total number of flutes may vary, and the flutes may be formed to extend either parallel to the longitudinal rotational axis of the tool or more commonly to extend about the rotational axis as a helix. In a helical arrangement, the cutting edges defined by the flutes are each described by a “helix angle,” which is the angle formed by a line tangent to the helix and a line parallel to the rotational axis of the tool.
Conventional rotary cutting tools perform adequately at conventional speeds (RPM) and feeds, however, at speeds and feeds higher than conventional, which is desirable for productivity, considerable performance decay is experienced. This performance decay is directly attributable to the presence and magnitude of vibration, specifically resonant vibration, as cutting force increases. At increased speeds and/or feeds, conventional helical and straight-fluted tools induce resonance, whereby the action of the tool cutting a workpiece has a tendency to enhance potential oscillatory energy when the frequency of the oscillations matches the system's natural frequency of vibration (its resonant frequency) or a harmonic thereof. The occurrence of uncontrolled resonant vibration inevitably results in a condition commonly referred to as “chatter,” which results in poor tool performance both in terms of life expectancy and workpiece quality. This is an undesirable occurrence.
Several approaches to solving the problem of chatter attempt to minimize the occurrence and resultant effect of resonant frequency vibration by increasing the stiffness of the cutting tool. For example, a single cemented tungsten carbide rod may be used to add stiffness to a rotary cutting tool. Unfortunately, the tungsten carbide rod is susceptible to cracking when subjected to side impact loads.